The present application is based on and claims priority from Japanese Patent Application 2000-225335 filed Jul. 26, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a brush-less rotary electric machine for a vehicle such as a passenger car or a truck.
2. Description of the Related Art
Usually, a vehicle AC generator has a field coil mounted on the rotor thereof. Accordingly, such an AC generator has a pair of slip rings, a pair of brushes and the brush holder thereof. Due to recent increase in the output power, increase in abrasion rate of the slip rings and the brushes and increase in heat generation by such a rotary power supply unit have become obstacles to providing a more powerful vehicle AC generator.
Although a brush-less AC generator that has a stationary field coil is well known, the stationary field coil is subject to muddy water, dust or the like, thereby causing gradual failure of insulation members of the field coil such as breakdown or short-circuiting of the field coil. Such a brush-less AC generator can not provide a sufficient amount of air for cooling the armature coil thereof because it is almost impossible to provide the rotor core with a pair of cooling fans due to the specific structure. In addition, a pole support ring, a large number of turns of field coil, etc. cause a high draft resistance of the cooling air passages inside the brush-less AC generator.
Therefore, the main object of the invention is to provide a reliable and powerful brush-less rotary electric machine that can provide a sufficient cooling air for the armature coil thereof.
According to a main aspect of the invention, a brush-less rotary electric machine includes a frame having a first and second walls and a pair of bearings fixed to the first and second walls, a stator core fixed to the frame, an armature coil formed of a plurality of U-shaped conductor segments having turn portions forming a first coil end and connection ends connected to one another to form a second coil end, a rotor shaft, a generally cylindrical stationary yoke, a rotary yoke disposed opposite the stationary yoke and fixed to the rotor shaft, a plurality of first claw pole members disposed opposite the inner periphery of the stator core, a plurality of second claw pole members fixed to the first claw pole members by a non-magnetic support member and disposed opposite the outer periphery of the stationary yoke, and a field coil fixed to the stationary yoke around the rotary yoke. The armature coil has a plurality of radial air passages at the second coil end, and the plurality of second claw pole members has a projection portion disposed close to the second wall.
Accordingly, the draft resistance of cooling passages in the coil end is reduced, and a plurality of upright side walls is formed at the plurality of second claw pole members. As a result, the armature coil can be cooled sufficiently, and muddy water and dust can be effectively discharged from the inside of the rotary electric machine.
According to another feature of the invention the connection ends are disposed opposite the plurality of second claw pole members. Therefore, the armature coil can be cooled more effectively.
According to another feature of the invention, each of the second claw pole members has a tapered projection portion disposed opposite the second coil end. This feature reduces the centrifugal force applied to the second claw pole members when the second claw pole members rotate.
According to another feature of the invention, the plurality of second claw pole members is supported at the projection portion by an annular magnetic member. This feature not only reinforces the second claw pole members against the centrifugal force during the rotation but reduces magnetic resistance of the air gap between the claw pole members and the stationary yoke.
According to another feature of the invention, the stationary yoke is fixed to the second wall. Therefore, a portion of the bearing can be utilized as a portion of the magnetic path, thereby providing a compact magnetic path.
According to another feature of the invention, the stationary yoke is disposed to abut the bearing fixed to the second wall. Therefore an additional retaining member for the bearing can be omitted.